Vegetable oils are typically oil that has been pressed or extracted, such as from a vegetable source. Many vegetable oils contain some form of phosphatides (e.g., hydratable or non-hydratable), commonly known as gums. For instance, soybean oil contains about 1-3%, corn oil 0.6-0.9%, sunflower oil 0.5-0.9%, and canola oil (crude) 1-3% of gums.
Gums can be partially or totally removed from vegetable oils through several different known degumming processes. The most commonly used processes in the industry are water degumming, acid degumming, caustic refining and enzymatic degumming, for example, as disclosed in U.S. Pat. Nos. 4,049,686; 5,239,096; 5,264,367; 5,286,886; 6,001,640; 6,033,706; 7,494,676 and 7,544,820, and U.S. Pat. Pub. Nos. 2007/0134777; 2008/0182322 and 2012/0258017.
A method disclosed in U.S. Pat. No. 4,240,972 discloses adding an acid to a heated stream of crude vegetable oil and then immediately passing the mixture through a static mixer to produce an acid-in-oil dispersion, and then separating the dispersion into an oil phase and an aqueous phase containing the phosphatides. This method claims that producing ultrafine acid droplets eliminates the need for lengthy acid-oil contact times. In another example, U.S. Pat. No. 4,698,185 describes a vegetable oil refining method with the steps of dispersing an aqueous organic acid in a water-degummed oil to form an acid-in-oil dispersion, allowing the phases to remain in contact for a time sufficient to decompose metal salts of phosphatidic acid, adding a base to the acid-in-oil dispersion to increase pH to above 2.5 without substantial formation of soap, and finally separating the dispersion into an oil phase and an aqueous phase containing the phosphatides.
Yet another method, as disclosed in U.S. Pat. No. 6,844,458, vegetable oil is combined with organic acid and subjecting to shearing to disperse the acid solution in the oil. The resulting acid-and-oil mixture is further mixed for a time sufficient to sequester contaminants into a hydrated impurities phase, producing a purified vegetable oil phase.
U.S. Pat. Pub. No. 2013/0011887 describes a method for hydration of non-hydratable phospholipids in an oil by mixing an aqueous acid with the oil to obtain an acidic mixture having pH of less than about 4, and mixing a base with the acidic mixture to obtain a reacted mixture having pH of about 6-9, wherein the mixing in steps creates an emulsion that has about 60% of an aqueous phase by volume in a droplet size between 15 μm to 45 μm in size.
The above-noted processes have the disadvantage that they have high oil yield losses, for example 3%, which also have impact the economics of the process. Accordingly, there is a continuing need for alternative refining methods, which can provide cost-effective removal of phosphorous, with improved oil yield.